Buffer

Abstract

In buffers, the deterioration of the buffer is suppressed to prevent a decrease in buffering function. [Solution] A buffer body to be attached to a radioactive material storage container, comprising: an impact absorber composed of a combination of multiple buffer materials; a covering material that covers the outer surface of the buffer material; and an outer shell member that covers the impact absorber from the outside.

Description

Technical Field

[0001] The present disclosure relates to a shock absorber mounted on a radioactive material storage container.

Background Art

[0002] In nuclear facilities, radioactive waste such as spent fuel generated in nuclear reactors and the like is stored in radioactive material storage containers, transported to storage facilities, reprocessing facilities and the like, and then stored or reprocessed. The radioactive material storage container is composed of a cask main body having a bottomed cylindrical shape with an open top, and a lid part fixed to the upper part of the cask main body to close the opening. The radioactive material storage container is provided with shock absorbers during transportation and storage. The shock absorber is attached to the axial end of the radioactive material storage container. The shock absorber absorbs impact by deforming when the radioactive material storage container is dropped, overturned, or collided.

[0003] As a shock absorber to be mounted on a radioactive material storage container, for example, there is one described in Patent Document 1.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0005] A shock absorber is generally configured by covering a cushioning material such as wood with a metal plate. The shock absorber may deteriorate after long-term use depending on the materials used and the usage environment. That is, since the radioactive material storage container stores radioactive waste, it reaches a high temperature, and heat is transferred from the radioactive material storage container to the shock absorber, causing the temperature of the shock absorber to rise, which may accelerate deterioration. In addition, although the cushioning material used for the shock absorber is controlled to have a moisture content not higher than a predetermined value, the moisture content may fluctuate due to temperature rise, which may accelerate deterioration.

[0006] This disclosure aims to solve the aforementioned problems and to provide a buffer that suppresses the decline in buffering function by suppressing deterioration. [Means for solving the problem]

[0007] The buffer body of this disclosure for achieving the above objective is a buffer body to be attached to a radioactive material storage container, comprising: an impact absorber composed of a plurality of buffer materials combined; a covering material that covers the outer surface of the buffer material; and an outer shell member that covers the impact absorber from the outside. [Effects of the Invention]

[0008] According to the buffer material of this disclosure, deterioration can be suppressed, thereby preventing a decrease in the buffering function. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a partially cutaway schematic diagram showing the internal structure of a radioactive material storage container. [Figure 2] Figure 2 is a cross-sectional view of the radioactive material storage container along its radial direction. [Figure 3] Figure 3 is a front view showing a radioactive material storage container with a buffer attached in a horizontal position. [Figure 4] Figure 4 is a plan view of the buffer installed in the radioactive material storage container. [Figure 5] Figure 5 is a VV cross-sectional view of Figure 4, showing the internal structure of the buffer. [Figure 6] Figure 6 is a plan view showing the buffer body of the first embodiment installed in a radioactive material storage container. [Figure 7] Figure 7 is a cross-sectional view taken along line VII-VII of Figure 6, showing the internal structure of the buffer. [Figure 8] Figure 8 is a perspective view showing a cushioning material covered with a heat-dissipating coating material. [Figure 9] Figure 9 is a perspective view showing a cushioning material covered with a modified covering material. [Figure 10] Figure 10 is a perspective view showing a cushioning material covered with a coating material that has moisture-resistant properties. [Figure 11] Figure 11 is a schematic diagram showing the buffer body of the second embodiment installed in a radioactive material storage container. [Figure 12] Figure 12 is a schematic diagram showing the buffer body of the third embodiment installed in a radioactive material storage container. [Modes for carrying out the invention]

[0010] Preferred embodiments of the present disclosure will be described in detail below with reference to the drawings. However, these embodiments do not limit the present disclosure, and where there are multiple embodiments, they may be combinations of these embodiments. Furthermore, the components in the embodiments include those readily conceivable by those skilled in the art, those that are substantially identical, and those that are equivalent.

[0011] [First Embodiment] <Radioactive material storage container> Figure 1 is a partially cutaway schematic diagram showing the internal structure of a radioactive material storage container, and Figure 2 is a cross-sectional view along the radial direction of the radioactive material storage container.

[0012] As shown in Figures 1 and 2, the cask 11, as a radioactive material storage container, comprises a cask body 12 and a lid 13. The cask body 12 has a body shell 21. The body shell 21 is cylindrical (in this embodiment, cylindrical in shape), with an opening 22 at its upper end and a closed lower end. The body shell 21 has a cavity 23 inside, and a basket 24 is placed in the cavity 23. The basket 24 is provided with a plurality of cells (storage compartments) 25 capable of individually storing radioactive materials (e.g., spent fuel assemblies). The body shell 21 is a forged product of carbon steel having a gamma-ray shielding function. However, stainless steel may be used instead of carbon steel for the body shell 21. Alternatively, the body shell 21 may be a casting of spheroidal graphite cast iron or carbon steel cast steel.

[0013] In the cask main body 12, an outer cylinder 26 is arranged with a gap on the outer peripheral surface of the main body barrel 21. Between the outer peripheral surface of the main body barrel 21 and the inner peripheral surface of the outer cylinder 26, a plurality of copper heat transfer fins 27 for heat conduction are provided at intervals in the circumferential direction. In the cask main body 12, a resin 28 as a neutron shield is arranged in the space surrounded by the main body barrel 21, the outer cylinder 26 and the heat transfer fins 27. The resin 28 is a polymer material containing a large amount of hydrogen, and contains boron or a boron compound having a neutron shielding function.

[0014] The cask main body 12 is provided with a bottom portion 29 protruding downward from the closed lower end of the main body barrel 21. The bottom portion 29 has a space surrounded by the closed lower end of the main body barrel 21, and a resin (neutron shield) is arranged in the space.

[0015] In the cask main body 12, trunnions 30 for lifting the cask 11 are provided on the main body barrel 21 at the upper portion and the lower portion of the cask 11 at a 90-degree pitch or a 180-degree pitch. The trunnion 30 is provided to penetrate the outer cylinder 26 from the main body barrel 21. The trunnion 30 protrudes to the outermost peripheral side of the cask 11.

[0016] The lid portion 13 is arranged at the opening 22 of the main body barrel 21. The lid portion 13 closes the opening 22 to hermetically seal the main body barrel 21 (cask main body 12). The lid portion 13 has a primary lid 31, a secondary lid 32, and a tertiary lid 33. The primary lid 31 is formed in a disc shape using carbon steel or stainless steel that shields γ-rays as a material. The secondary lid 32 covers the primary lid 31 and is exposed to the outside of the cask 11, and like the primary lid 31, is formed in a disc shape using carbon steel or stainless steel that shields γ-rays as a material. A resin (neutron shield) 28 may be provided between the primary lid 31 and the secondary lid 32. The tertiary lid 33 is provided on the outer side of the secondary lid 32, but the tertiary lid 33 may be omitted. Like the primary lid 31 and the secondary lid 32, the tertiary lid 33 is formed in a disc shape using carbon steel or stainless steel that shields γ-rays as a material.

[0017] The primary cover 31 is fixed to the first stage portion 22a formed in the opening 22 of the main body 21 by bolts (not shown) made of carbon steel or stainless steel. The secondary cover 32 is fixed to the second stage portion 22b formed in the opening 22 of the main body 21 by bolts (not shown) made of carbon steel or stainless steel. Although not shown, metal gaskets are provided between the primary cover 31 and the first stage portion 22a and between the secondary cover 32 and the second stage portion 22b. The metal gaskets ensure airtightness between the primary cover 31 and the first stage portion 22a and between the secondary cover 32 and the second stage portion 22b. The tertiary cover 33 is fixed to the first stage portion 22c formed in the opening 22 of the main body 21 by bolts (not shown) made of carbon steel or stainless steel. A rubber O-ring is provided between the tertiary cover 33 and the main body 21 to ensure airtightness.

[0018] In a nuclear power plant, for example, multiple spent fuel assemblies are stored in the cells 25 of the basket 24 of the main body 21 of the cask 11, and sealed by the lid 13. The cask 11 is transported, for example, from the nuclear power plant to a storage facility. During transport, the cask 11 is fitted with transport buffers (not shown). The transport buffers are fitted to the top and bottom of the cask body 12. The cask 11 is loaded on its side on the bed of a transport vehicle and transported to the storage facility.

[0019] <Placement of radioactive material storage containers> Figure 3 is a front view showing a radioactive material storage container with a buffer attached in a horizontal position.

[0020] As shown in Figure 3, the cask 11 can be fitted with buffers 41 and 42 at its axial ends. Buffer 41 is fitted to the bottom 29 of the cask body 12, which is one axial end of the cask 11, and buffer 42 is fitted to the lid 13, which is the other axial end of the cask 11.

[0021] In a nuclear power plant, for example, spent fuel assemblies are stored in the cells 25 (see Figure 1) of the basket 24 of the main body shell 21 of the cask 11, and sealed by the lid 13. The cask 11 is transported, for example, from the nuclear power plant to a storage facility. A transport buffer (not shown) is attached to the cask 11 during transport. When the cask 11 is transported to the storage facility, the transport buffer is removed, a buffer 41 is attached to the bottom 29 of the cask body 12, and a buffer 42 is attached to the lid 13. Alternatively, the cask may be transported with buffer 41 attached instead of the transport buffer. The buffers 41 and 42 are transport buffers, but they may also be storage buffers.

[0022] The cask 11 is stored in a horizontal position with its central axis O aligned horizontally, with the cushioning bodies 41 and 42 attached. The cask 11 is supported on a stand 43 in a horizontal position. The stand 43 is provided with a plurality of support parts 44, and the cask 11 is supported, for example, by each trunnion 30 on a support part 44. However, the cask 11 may also be supported by the cask body 12. The cask 11 is stored in a horizontal position with its central axis O aligned horizontally by the stand 43. In this case, the cask 11 has the cushioning body 41 attached to one side (lid part 13 side) along the central axis O, and the cushioning body 42 attached to the other side (lid part 13 side) along the central axis O. The cushioning bodies 41 and 42 have substantially the same configuration.

[0023] The cask 11 may also be stored in a vertical position with its central axis O aligned vertically. In this case, the cask 11 is placed vertically with its lid 13 facing upwards, and a buffer 42 is attached to the lid 13 side. When stored, the cask 11 is fitted into a frame (not shown) at its bottom 29, or fixed to a frame by securing the trunnion, and stored in a vertical position with its central axis O aligned vertically.

[0024] <Buffer> Figure 4 is a plan view of the buffer attached to the radioactive material storage container, and Figure 5 is a cross-sectional view of Figure 4, VV, showing the internal structure of the buffer. Note that the buffers 41 and 42 described above have almost the same structure, and below we will describe in detail the buffer 42 attached to the lid 13 of the cask body 12 in the cask 11.

[0025] The buffer 42 comprises a structure 51, an outer shell member 52, and a shock absorber 53. The shock absorber 53 is positioned on the outside of the structure 51, and the outer shell member 52 covers the shock absorber 53 from the outside and is fixed to the structure 51. The buffer 42 is fixed to the lid 13 of the cask body 12 of the cask 11 by a plurality of bolts (not shown).

[0026] The structure 51 is composed of disc members 61, cylindrical members 62, and the like.

[0027] A cylindrical member 62 is connected to one of the flat surfaces of the disc member 61.

[0028] The outer shell member 52 has a disc portion 71 and a cylindrical portion 72. One end of the cylindrical portion 72 is integrally connected to the outer circumference of the disc portion 71 in the axial direction. The outer shell member 52 is made of a metal plate such as a steel plate and has a hollow shape, and is deformable by a predetermined load. The predetermined load is the load of the falling object that is assumed to fall, or the load that acts on the cask 11 when the cask 11 falls. The outer diameter of the outer shell member 52 is larger than the outer diameter of the cask 11.

[0029] The shock absorber 53 is positioned on the outer axial and radial sides of the structure 51. The shock absorber 53 absorbs the impact generated when the cask 11 falls or collides by deforming. The shock absorber 53 is composed of multiple cushioning materials. The cushioning materials deform under a predetermined load and are preferably composed of materials such as wood, foam, polymer compounds, or porous materials. The multiple cushioning materials are, for example, blocks of wood, and the shock absorber 53 is formed by combining multiple blocks. The multiple blocks are divided in the circumferential and axial directions. Furthermore, it is preferable to place blocks with different strengths depending on their location.

[0030] The buffer body 42 is fixed to the lid portion 13 of the cask body 12 by multiple bolts 81. The shock absorber 53 consists of multiple tubular members 82 arranged at intervals in the circumferential direction, oriented axially. One end of each tubular member 82 in the axial direction is connected to the disc member 61 of the structure 51, and the other end in the axial direction is connected to the disc portion 71 of the outer shell member 52. Through holes 71a are formed in the disc portion 71 at the connection points of the tubular members 82. The buffer body 42 is fixed by multiple bolts 81 when the structure 51 is fitted to the bottom of the cask body. The bolts 81 are inserted from the outside of the buffer body 42 in the order of through holes 71a in the disc portion 71 and then the tubular members 82, with their tips passing through the mounting holes in the disc member 61 and screwed into the threaded holes of the lid portion 13.

[0031] <Specific composition of the buffer> Figure 6 is a plan view showing the buffer body of the first embodiment installed in a radioactive material storage container, and Figure 7 is a cross-sectional view taken along line VII-VII of Figure 6, showing the internal structure of the buffer body.

[0032] The buffers 41 and 42 are attached to the cask 11. The cask 11 becomes hot because it contains radioactive waste. As a result, the temperature of the buffers 41 and 42 rises as heat from the cask 11 is transferred to them. The buffers 41 and 42 are constructed by covering an impact absorber 53, which is placed on the outside of the structure 51, with an outer shell member 52, and the impact absorber 53 is kept in a state of isolation from the outside air.

[0033] The shock absorber 53 is composed of wood, foam, polymer compounds, porous materials, etc. The buffer 42 deteriorates with long-term use depending on the materials used and the environment in which it is used. For example, the buffer material that makes up the shock absorber 53 may deteriorate due to changes in temperature and humidity. Temperature and humidity may fluctuate depending on the surrounding environment, and an increase in the temperature and humidity of the buffer material may accelerate deterioration.

[0034] Therefore, as shown in Figures 6 and 7, the buffers 41 and 42 of the first embodiment have heat removal and dehumidification functions. The buffers 41 and 42 have almost the same configuration, and the buffer 42 will be described in detail.

[0035] The buffer body 42 comprises a structure 51, an outer shell member 52, and an impact absorber 53. The outer shell member 52 covers the impact absorber 53 from the outside and is fixed to the structure 51. The impact absorber 53 is composed of, for example, four types of cushioning materials 101a, 101b, 101c, and 101d. The types of cushioning materials 101a, 101b, 101c, and 101d are not limited to four types. The four types of cushioning materials 101a, 101b, 101c, and 101d may be composed of different materials or materials with different compressive strengths (densities). The cushioning material 101a is placed in the center of the buffer body 42. The cushioning material 101a is composed of a cylindrical cushioning material divided into six sections in the circumferential direction. Therefore, the cushioning material 101a has a fan shape when viewed from above.

[0036] The cushioning material 101b is positioned radially outside the cushioning material 101a. The cushioning material 101b is composed of a ring-shaped cushioning material divided, for example, into six sections in the circumferential direction. Each cushioning material 101b is positioned between each pipe member 82. The cushioning materials 101c and 101d are positioned radially outside the cushioning material 101b. The cushioning materials 101c and 101d are composed of a ring-shaped cushioning material divided into six sections in the circumferential direction. The cushioning materials 101c and 101d are positioned so as to overlap in the axial direction.

[0037] <Heat removal structure of buffer body> Figure 8 is a perspective view showing a cushioning material covered with a heat-dissipating covering material, and Figure 9 is a perspective view showing a cushioning material covered with a modified covering material. The shock absorber 53 is composed of, for example, four types of cushioning materials 101a, 101b, 101c, and 101d, but in Figures 8 and 9, it is described as a cubic cushioning material 101.

[0038] As shown in Figure 8, the cushioning body 42 has a heat dissipation structure, which includes a covering material 102 that covers the outer surface of the cushioning material 101. The covering material 102 is made of a metal material or graphene sheet with excellent thermal conductivity. Suitable metal materials include copper, iron, and aluminum. The covering material 102 has a box-like shape that covers the entire surface of the cushioning material 101. It is preferable that the box-shaped covering material 102 adheres closely to the entire surface of the cushioning material 101. It is preferable to make the thickness of the covering material 102 thin, taking into consideration the weight increase of the shock absorber 53. The covering material 102 may be, for example, a metal foil that is arranged in close contact with the entire surface of the cushioning material 101. In addition, the cushioning material 101 is in contact (preferably surface contact) with adjacent cushioning material 101 while covered with the covering material 102.

[0039] As shown in Figure 9, the buffer body 42 has a heat dissipation structure, which includes a covering material 103 that covers the outer surface of the buffer material 101. The covering material 103 is made of a metal material with excellent thermal conductivity. The covering material 103 has a box-like shape that covers the entire surface of the buffer material 101. The covering material 103 has a plurality of holes 104. By providing a plurality of holes 104, the covering material 103 can be made lighter.

[0040] <Dehumidifying structure of the buffer> Figure 10 is a perspective view showing a cushioning material covered with a coating material that has moisture-resistant properties.

[0041] As shown in Figure 10, the dehumidifying structure of the buffer body 42, similar to the heat removal structure, includes a covering material 105 that covers the outer surface of the cushioning material 101. The covering material 105 is made of a material with excellent moisture impermeability. Suitable materials with excellent moisture impermeability that prevent moisture from passing through include, for example, resin films and resin sheets. Before assembly, the cushioning material 101 is dried to remove moisture and has a predetermined moisture content (e.g., 13%) or less. The covering material 105 covers the dried cushioning material 101 so as to seal it. The covering material 105 has a box shape that covers the entire surface of the cushioning material 101. It is preferable that the box-shaped covering material 105 adheres tightly to the entire surface of the cushioning material 101. It is preferable to reduce the thickness of the covering material 105 considering the weight increase of the shock absorber 53.

[0042] The buffer 42 may have both heat removal and dehumidification functions. For example, the buffer 42 has covering materials 102 (103) and 105 that cover the outer surface of the buffer material 101. The buffer material 101 is double-covered by covering materials 102 (103) and 105. However, if the covering material is a material with excellent thermal conductivity and excellent moisture impermeability (for example, a metal-containing film or sheet such as a graphene sheet), then the buffer material 101 only needs to be covered by one covering material.

[0043] <The function of buffers> The buffers 41 and 42 are attached to the cask 11, and heat is transferred from the cask 11, causing their temperature to rise, which in turn causes the temperature of the multiple buffers 101 to rise. If the buffers 101 are covered by covering materials 102 and 103 that have a heat removal mechanism, the heat from the heated buffers 101 is transferred to the covering materials 102, 103, and 105, which have excellent thermal conductivity. Since the multiple buffers 101 are in contact with each other, adjacent buffers 101 and covering materials 102 and 103, heat is transferred between them. Since the multiple buffers 101 are in contact with the metal outer shell member 52, the heat from the multiple buffers 101 (covering materials 102 and 103) is transferred to the outer shell member 52 and released to the outside. As a result, the temperature of each buffer 101 in the shock absorber 53 of the buffers 41 and 42 decreases, and deterioration of the buffers 101 due to temperature rise is suppressed.

[0044] Furthermore, the heat from the cask 11 can cause the temperature and humidity of the surrounding air to rise. When the cushioning material 101 is covered with a covering material 105 that has a dehumidifying mechanism, the cushioning material 101 is prevented from coming into contact with the outside air by the covering material 105. As a result, humid air is blocked by the covering material 105, which has excellent moisture impermeability, and does not come into contact with the cushioning material 101, thus maintaining the dry state of the cushioning material 101. Therefore, the humidity of each cushioning material 101 in the shock absorber 53 of the cushioning bodies 41 and 42 does not assimilate, and deterioration of the cushioning material 101 due to rising humidity is suppressed.

[0045] In the above description, one cushioning material is covered with one covering material 102, 103, or 105, but the configuration is not limited to this. For example, multiple cushioning materials may be covered with one covering material 102, 103, or 105. In this case, it is preferable to cover multiple cushioning materials 101 of the same type or with the same compressive strength (density) with one covering material 102, 103, or 105. However, if multiple cushioning materials 101 of different types or with different compressive strengths (densities) are covered with one covering material 102, 103, or 105, a partition member may be placed inside to divide the room.

[0046] [Second Embodiment] Figure 11 is a schematic diagram showing the buffer body of the second embodiment installed in a radioactive material storage container. Components having the same function as those in the first embodiment described above are denoted by the same reference numerals, and detailed explanations are omitted.

[0047] As shown in Figure 11, the buffers 41A and 42A of the second embodiment have a heat removal function. The buffers 41A and 42A have almost the same configuration, and the buffer 42A will be described in detail.

[0048] The buffer body 42A has a structure 51 (see Figure 7), an outer shell member 52, and a shock absorber 53, and the shock absorber 53 has a buffer material 101 (101a, 101b, 101c, 101d, 101e) covered with a covering material 102 (see Figure 8) that has a heat dissipation function.

[0049] The buffer body 42A has a gas supply device 111 that supplies cooling gas to the inside. The outer shell member 52 has an inlet 52a at its lower vertical end and an outlet 52b at its upper end. The gas supply path 112 has its base end connected to the outlet 52b and its tip connected to the inlet 52a. Here, the cooling gas is, for example, air or nitrogen, and is preferably at a temperature lower than room temperature. The gas supply path 112 is equipped with a pump 113 and a flow control valve 114. The pump 113 is connected to a power supply unit 115. The pump 113 is driven by power supplied from the power supply unit 115 and circulates the cooling gas discharged from the outlet 52b to the inlet 52a via the gas supply path 112. The flow control valve 114 functions as an adjustment member that adjusts the flow rate of the cooling gas discharged from the buffer body 42A, and by adjusting the opening degree, it adjusts the pressure inside the buffer body 42A to a higher level.

[0050] Furthermore, a cooling device 116 is provided in the gas supply path 112. The cooling device 116 is, for example, a heat exchanger. The cooling device 116 is located downstream of the pump 113 in the gas supply path 112, but it may also be located upstream of the pump 113. The cooling device 116 cools the cooling gas supplied from the gas supply path 112 to the buffer body 42A, and supplies the buffer body 42A with cooling gas that is, for example, at a lower temperature than the outside air.

[0051] The power supply unit 115 may also be a power supply unit 115A having a thermoelectric element that can be attached to the cask 11. The thermoelectric element is flat and fixed to the outer surface of the cask 11. The thermoelectric element is, for example, a Peltier element. A Peltier element has P-type and N-type semiconductors joined to a metal electrode, and generates electricity when one flat surface is heated and the other flat surface is cooled, creating a temperature difference between the two flat surfaces. The thermoelectric element constituting the power supply unit 115A may be placed between the cask 11 and the buffer 42A. The gas supply device 111 is operated by the power generated by the power supply unit 115A having the thermoelectric element, with the pump 113 powered by the electricity.

[0052] <The heat-removing effect of buffers> The gas supply device 111 drives the pump 113 and supplies cooling gas from the gas supply path 112 to the inlet 52a of the buffer body 42A. The cooling gas supplied to the buffer body 42A cools the buffer materials 101a, 101b, 101c, 101d, and 101e that constitute the shock absorber 53 located inside the outer shell member 52. That is, the cooling gas cools the buffer materials 101a, 101b, 101c, 101d, and 101e as it rises between the covering material 102 that covers them. The cooling gas that has cooled the buffer materials 101a, 101b, 101c, 101d, and 101e is discharged from the outlet 52b into the gas supply path 112. Therefore, the cushioning materials 101a, 101b, 101c, 101d, and 101e are cooled, their temperature decreases, and deterioration is suppressed.

[0053] Although the base end of the gas supply path 112 is connected to the outlet 52b and the tip end is connected to the inlet 52a, the configuration is not limited to this. For example, the base end of the gas supply path 112 may be connected to the gas supply source for the cooling gas, and the tip end may be connected to the inlet 52a. In this case, the cooling gas from the gas supply source is continuously supplied to the inside of the buffer body 42A via the gas supply path 112 by driving the pump 113.

[0054] [Third Embodiment] Figure 12 is a schematic diagram showing the buffer body of the third embodiment installed in a radioactive material storage container. Components having the same function as those in the first embodiment described above are denoted by the same reference numerals, and detailed explanations are omitted.

[0055] As shown in Figure 12, the buffers 41B and 42B of the third embodiment have a dehumidifying function. The buffers 41B and 42B have almost the same configuration, and the buffer 42B will be described in detail.

[0056] The buffer body 42B has a structure 51 (see Figure 7), an outer shell member 52, and a shock absorber 53, and the shock absorber 53 has a buffer material 101 (101a, 101b, 101c, 101d, 101e) covered with a covering material 105 (see Figure 10) that has a dehumidifying function.

[0057] The buffer body 42B has a gas supply device 121 that supplies dry gas to the inside. The outer shell member 52 has an inlet 52a at its lower vertical end and an outlet 52b at its upper end. The gas supply path 122 has its base end connected to a gas supply source 123 for dry gas and its tip connected to the inlet 52a. Here, the dry gas is, for example, air or nitrogen, and from the viewpoint of heat removal, it is preferable that it is at a temperature lower than ambient temperature. The gas supply path 122 is equipped with a pump 124. The pump 124 is connected to a power supply unit 125. The pump 124 is driven by power supplied from the power supply unit 125 and supplies dry gas from the gas supply source 123 to the inlet 52a through the gas supply path 122. On the other hand, the buffer body 42B is equipped with a flow control valve 126 at the outlet 52b. The flow control valve 126 functions as an adjustment member that adjusts the flow rate of dry gas discharged from the buffer body 42B, and by adjusting the degree of opening, it adjusts the pressure inside the buffer body 42B to a higher level.

[0058] Furthermore, a dehumidifier 127 is provided in the gas supply path 122. The dehumidifier 127 is, for example, a desiccant. The dehumidifier 127 is located downstream of the pump 124 in the gas supply path 122, but it may also be located upstream of the pump 124. The dehumidifier 127 removes moisture from the dry gas supplied from the gas supply path 122 to the buffer body 42B, and supplies dry gas with a lower moisture content than the outside air to the buffer body 42B, for example.

[0059] The power supply unit 125 may also be a power supply unit 125A having a thermoelectric element (Peltier element) that can be attached to the cask 11. Furthermore, the gas supply path 122 may be a circulation path connecting the inlet 52a and outlet 52b of the buffer body 42B.

[0060] <Dehumidifying effect of buffer material> The gas supply device 121 drives the pump 124 and supplies dry gas from the gas supply source 123 to the inlet 121a of the buffer body 42B via the gas supply path 122. The dry gas supplied to the buffer body 42B cools the buffer materials 101a, 101b, 101c, 101d, and 101e that constitute the shock absorber 53 located inside the outer shell member 52. That is, the dry gas dehumidifies as it rises between the covering material 105 that covers the buffer materials 101a, 101b, 101c, 101d, and 101e. The dehumidified dry gas is discharged from the outlet 52b into the gas supply path 122. As a result, the air outside the covering material 105 of the buffer materials 101a, 101b, 101c, 101d, and 101e is dehumidified, the humidity decreases, and deterioration is suppressed.

[0061] [Effects of this embodiment] The buffer body according to the first embodiment is a buffer body 41, 41A, 41B, 42, 42A, 42B to be attached to a cask (radioactive material storage container) 11, comprising a shock absorber 53 composed of a plurality of buffer materials 101 (101a, 101b, 101c, 101d, 101e) combined together, covering materials 102, 103, 105 that cover the outer surface of the buffer material 101, and an outer shell member 52 that covers the shock absorber 53 from the outside.

[0062] According to the first embodiment of the buffer, since the multiple buffer materials 101 constituting the shock absorber 53 are covered by the covering materials 102, 103, and 105, the rise in temperature and humidity can be suppressed. Therefore, the rise in temperature and humidity of the buffer material 101 can be suppressed, and deterioration can be suppressed, thereby preventing a decrease in the buffering function.

[0063] The buffer according to the second embodiment is the buffer according to the first embodiment, further wherein the covering materials 102 and 103 are made of a metal material. As a result, the heat from the buffer material 101 is transferred to the metal covering materials 102 and 103 and then released to the outside, thereby suppressing the temperature rise of the buffer material 101.

[0064] The third embodiment of the buffer is a buffer according to the first or second embodiment, and further, the covering material 103 has holes 104. This makes it possible to reduce the weight of the covering material 103.

[0065] The buffer according to the fourth embodiment is a buffer according to any one of the first to third embodiments, and further includes a gas supply device 111 that supplies cooling gas inside the outer shell member 52. This makes it possible to suppress the temperature rise of the buffer material 101.

[0066] The buffer according to the fifth embodiment is a buffer according to any one of the first to fourth embodiments, and further, the covering material 105 is formed of an impermeable material that prevents moisture from passing through. As a result, the buffer material 101 does not come into contact with the outside air, and the increase in humidity of the buffer material 101 can be suppressed.

[0067] The buffer according to the sixth embodiment is a buffer according to any one of the first to fifth embodiments, and furthermore, the covering material 105 covers the buffer material 101 in a way that it is airtight. This makes it possible to prevent the buffer material 101 from coming into contact with the outside air.

[0068] The buffer according to the seventh embodiment is a buffer according to any one of the first to sixth embodiments, and further includes a gas supply device 121 that supplies dry gas inside the outer shell member 52. This makes it possible to suppress the rise in humidity of the buffer material 101.

[0069] The buffer according to the eighth embodiment is the buffer according to the seventh embodiment, further comprising a gas supply device 121 that supplies dry gas into the interior of the outer shell member 52 and discharges the internal gas to the outside. This allows the interior of the outer shell member 52 to be replaced with dry gas, and the moisture content of the buffer material 101 can be maintained at an optimal value.

[0070] The buffer according to the ninth embodiment is a buffer according to the seventh or eighth embodiment, and further, the gas supply device 121 maintains the internal pressure of the outer shell member 52 higher than the external pressure. By maintaining a high internal pressure of the outer shell member 52, it is possible to prevent external air from entering the inside of the outer shell member 52 and maintain the moisture content of the buffer material 101 at an optimal value.

[0071] The buffer according to the tenth embodiment is a buffer according to the fourth or seventh embodiment, further having a thermoelectric element that can be attached to the cask 11, and the gas supply devices 111 and 121 are operated by the electricity generated by the thermoelectric element. This makes it possible to secure power for the gas supply devices 111 and 121 using the heat of the cask 11, and simplifies the device by eliminating the need for a separate power supply unit. [Explanation of symbols]

[0072] 11. Cask (container for radioactive material) 12 Cask body 13 Lid 29 Bottom 31 Primary lid 32 Secondary lid 41,41A,41B,42,42A,42B buffer 43. Stand 44 Support part 51 Structure 52 Outer shell member 53 Shock absorber 101,101a,101b,101c,101d,101e Cushioning material 102,103,105 Covering material 104 Hole 111,121 Gas supply equipment 112,122 Gas supply routes 113,124 pumps 114,126 Flow control valve 115,125,125A power supply section 116 Cooling device 123 Gas supply sources 127 Dehumidifier

Claims

1. A buffer to be attached to a container for radioactive materials, An impact absorber composed of multiple cushioning materials, A covering material that covers the outer surface of the cushioning material, An outer shell member that covers the aforementioned shock absorber from the outside, A buffer equipped with the following features.

2. The aforementioned covering material is formed from a metal material. The buffer according to claim 1.

3. The covering material has holes, The buffer according to claim 1.

4. A gas supply device is provided to supply cooling gas to the inside of the outer shell member. The buffer according to claim 2.

5. The coating material is formed of an impermeable material that prevents moisture from passing through. The buffer according to claim 1.

6. The covering material covers the cushioning material in a way that it is airtight. The buffer according to claim 1.

7. A gas supply device is provided to supply drying gas to the inside of the outer shell member. The buffer according to claim 5.

8. The gas supply device supplies dry gas into the interior of the outer shell member and discharges the gas from the interior to the outside. The buffer according to claim 7.

9. The gas supply device maintains the internal pressure of the outer shell member higher than the external pressure. The buffer according to claim 8.

10. The gas supply device has a thermoelectric element that can be attached to the radioactive material storage container, and the gas supply device operates using electricity generated by the thermoelectric element. The buffer according to claim 4 or claim 7.

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